1. Technical Field
The present invention relates to nuts, and more particularly, to decorative capped wheel nuts of the type including a nut body or nut insert having a sheet metal cap welded thereto which may be used for holding a wheel on a motor vehicle or the like where the capped wheel nut is visible and may be exposed to the environment.
2. Description of the Prior Art
Wheel nuts, capped nuts, capped wheel nuts and the like have been described in the literature for many years and are disclosed, for example, in U.S. Pats. Nos. 2,391,989, Luce; 3,364,806, Chaivre; 3,585,900, Chaivre; 4,018,133, Chaivre; 4,123,961, Jadach; 3,955,231, Erdmann; and United Kingdom Patent Specification No. 739,405, Allmanna. By way of further elaboration, U.S. Pat. No. 2,391,989 to Luce discloses a threaded locking device such as a nut having a lateral flange at the bottom. A sheet metal "cap," open at the top, has a lower lateral flange, the underside of which is welded, at the bottom of the nut, to the upper surface of the nut flange. U.S. Pat. No. 4,018,133, to Chaivre, discloses a capped wheel nut where the cap may be adhesively secured to the nut or welded to the nut. U.S. Pat. No. 154,255, to Ives, discloses a carriage axle nut provided with a cap with the cap secured to the nut by brazing. U.S. Pat. No. 4,275,285, to Jadach, discloses a capped wheel nut with the cap welded to the nut body at the wrench flats.
Particular attention is also directed to U.S. Pat. No. 4,123,961, to Jadach, which discloses a decorative nut for holding a wheel on a motor vehicle and which is exposed to view on the wheel and exposed to the environment. A nut insert or nut body is sheathed by a stainless steel cap which projects over the top of the nut insert and down the wrench flats, and the cap is welded to the nut insert. In the embodiments of FIGS. 1-9 of that patent, the weld occurs between the cap and the nut insert essentially at the top of the nut insert. In the embodiment of FIG. 10, the bottom of the nut insert or nut body has a flange, and the cap has a flange; the underside of the cap flange is welded to the upper surface of the nut body flange at the bottom of the nut body.
Several limitations have been associated with welded capped wheel nuts of the types described. One significant limitation has been that the wheel nuts are not completely sealed against moisture entering underneath the cap where corrosion may occur to peal sides of the cap away from the nut insert. Entry of moisture is facilitated by the capillary action of the water entering between the cap and the nut. One known type of capped wheel nut includes a ring shaped welding projection on the outer end of the nut body which results in a ring shaped weld between the nut body and the cap. Although such a weld may prevent moisture from entering the threads of the nut body, it nevertheless allows moisture to enter between the cap along the sides of the nut body, resulting in the cap "peeling" as mentioned above.
Also, a manufacturing limitation is the control of the welding current when relatively large lateral surface areas are welded together such as described in the aforementioned U.S. Pat. No. 4,123,961. While this problem has been reduced by the use of spot welding, such as described in U.S. Pat. No. 2,391,989, or by the provision of individual, spaced welding nibs at the top of the nut insert, neither spot welding nor individual welding nibs solves the aforementioned moisture problem. Of course, while buffing or polishing may be technologically feasible to overcome any problem of discoloration, such buffing or polishing necessarily increases the manufacturing cost of a welded capped wheel nut.